Our Star The Sun
Our Star the Sun
The sun, our star, is a type G yellow dwarf. As stars go, it is unimpressive. Yet to life on Earth it is essential.
Our sun is about half way through its life cycle, having originated out of a cloud of gas about five and a half billion years ago. In about another five to six billion years it will run out of fuel
Photo Credit: NASA
How the Sun Works
Hydrogen, under immense temperature and pressure, can be fused into helium. This fusion releases energy. That energy can then travel through space and provide energy to the planets.
The fusion process is not simple. One cannot just push hydrogen together. Two of the hydrogen nuclei, protons, must be converted to neutrons. This requires electrons. The source of these electrons is often from energy being converted to a positron-electron pair. In fact, there are several processes that go on, but the result is always the same, helium and a release of energy.
When enough material gathered from the cloud of gas and collapsed under gravity, deep inside the sun the fusion process turned on. It is migrating outward, leaving behind a sphere of helium. One day, the explosive force will be strong enough to overcome gravity, and our sun will explode. But that day is not about to happen soon.
The Universe, a History Channel Series, covered the sun in Season 1, which is now available for sale.
The Universe: A Guided Tour is another video that is well done. It is slightly older, but still current. It gives some different details.
Most of the information contained here is from these sources.
The Sun Is a Complex Place
The sun is not a smooth glowing object. It is hot, and boiling. Its surface is always changing as large convection cells rush material from its interior to its surface.
The sun has currents beneath its surface that move material from one place to another, sometimes at great speeds.
The sun has a magnetic field that reverses about every eleven years. During that eleven years the sun goes through high and low activity. Near the reversal, the activity is high. This means an increase in solar flares, sunspots, and release of charged particles.
A sunspot cycle is twenty-two years long, but it is effectively eleven years long. Sunspots break out in rough lines in both the northern and southern hemispheres. These lines move in the direction of the equator. Along the way sunspots come and go. They never reach the equator before the next line forms, and briefly two lines are present at the same time.
Sunspots are dark spots on the sun. This is because they are cooler than their surroundings, but are highly energetic. They are, in fact, magnetic storms that have charged particles rotation. The direction of the rotation depends on the magnetic field.
Sunspots and Earth
Sunspots have often been associated with climate. It appears the Earth is warmer during high sunspot activity, and cooler otherwise. There was a period during the Little Ice Age when the sun ceased making spots.
High solar activity is also associated with the aurora displays, also known as the Northern and Southern lights.
Type G stars eventually run out of hydrogen and began to fuse helium into even heavier material. The star cools. This causes it to shrink, and a fusion of helium starts. It grows into a red giant, which in the case of the sun is about to the Earth’s orbit, releases energy, and collapses into a brown or white dwarf. Eventually, even the dwarf star runs out of energy, and it goes dark.
Our sun is not massive enough to ever become a black hole.